This invention relates to a nacelle assembly for a gas turbine engine, particularly for an aircraft.
For a gas turbine engine, such as a turbo fan engine, air is pressurized in a compressor and mixed with fuel in a combustor to generate hot combustion gases. These gases flow downstream through the turbine stages of the engine, which extract energy from the gases. In a two spool gas turbine engine, a high pressure turbine powers a high pressure compressor, while a low pressure turbine powers the fan section disposed upstream of the compressor and a low pressure compressor.
Combustion gases are discharged from the turbo fan engine through a core exhaust nozzle while fan air is discharged through an annular fan exhaust nozzle defined at least partially by a nacelle surrounding the core engine. A majority of the propulsion thrust is provided by the pressurized fan air, which is discharged through the fan exhaust nozzle. The remaining thrust is provided by the combustion gases discharged through the core exhaust nozzle.
It is known in the field of aircraft gas turbine engines that the performance of the turbo fan engine varies during diverse flight conditions experienced by the aircraft. An inlet lip section located at the foremost edge of the turbo fan nacelle is typically designed to enable operation of the turbo fan engine and prevent the separation of airflow from the inlet lip section of the nacelle during these diverse flight conditions. For example, the inlet lip section requires a “thick” inlet lip section designed to support operation of the turbo fan during specific flight conditions, such as cross-wind conditions, take-off and the like. Disadvantageously, the “thick” inlet lip section may reduce the efficiency of the turbo fan engine during cruise conditions of the aircraft, which exist for the large majority of the flight of the aircraft.
A need therefore exists to optimize the performance of a turbo fan gas turbine engine during diverse flight conditions so as to reduce the nacelle thickness and its associated drag.